When traveling with pets, many people allow their pets to stick their heads out of car (or truck) windows, either with the window partially open or, while holding the pet, with the window wide open. Additionally, people often leave their pets in the car unattended, either with the window partially open or completely closed.
In passenger cars with windows partially open, pets risk injury to the head or paws, should automatic windows get activated by mistake. Also should the car suddenly brake, pets might be thrown against the glass of the window.
In passenger cars with windows wide open, pets risk being ejected or could jump out of vehicles. As pets stick their heads out of windows too far out, they could get injured by other vehicles or objects.
In passenger cars with windows closed, pets could suffer from overheating and lack of ventilation.